/*
     This file is part of GNUnet.
     Copyright (C) 2010 GNUnet e.V.

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
*/

/**
 * @author Christian Grothoff
 *
 * @file
 * Library for data block manipulation
 *
 * @defgroup block  Block library
 * Library for data block manipulation
 * @{
 */
#ifndef GNUNET_BLOCK_LIB_H
#define GNUNET_BLOCK_LIB_H

#include "gnunet_util_lib.h"
#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif


/**
 * Blocks in the datastore and the datacache must have a unique type.
 */
enum GNUNET_BLOCK_Type
{
  /**
   * Any type of block, used as a wildcard when searching.  Should
   * never be attached to a specific block.
   */
  GNUNET_BLOCK_TYPE_ANY = 0,

  /**
   * Data block (leaf) in the CHK tree.
   */
  GNUNET_BLOCK_TYPE_FS_DBLOCK = 1,

  /**
   * Inner block in the CHK tree.
   */
  GNUNET_BLOCK_TYPE_FS_IBLOCK = 2,

  /**
   * Legacy type, no longer in use.
   */
  GNUNET_BLOCK_TYPE_FS_KBLOCK = 3,

  /**
   * Legacy type, no longer in use.
   */
  GNUNET_BLOCK_TYPE_FS_SBLOCK = 4,

  /**
   * Legacy type, no longer in use.
   */
  GNUNET_BLOCK_TYPE_FS_NBLOCK = 5,

  /**
   * Type of a block representing a block to be encoded on demand from disk.
   * Should never appear on the network directly.
   */
  GNUNET_BLOCK_TYPE_FS_ONDEMAND = 6,

  /**
   * Type of a block that contains a HELLO for a peer (for
   * DHT and CADET find-peer operations).
   */
  GNUNET_BLOCK_TYPE_DHT_HELLO = 7,

  /**
   * Block for testing.
   */
  GNUNET_BLOCK_TYPE_TEST = 8,

  /**
   * Type of a block representing any type of search result
   * (universal).  Implemented in the context of #2564, replaces
   * SBLOCKS, KBLOCKS and NBLOCKS.
   */
  GNUNET_BLOCK_TYPE_FS_UBLOCK = 9,

  /**
   * Block for storing DNS exit service advertisements.
   */
  GNUNET_BLOCK_TYPE_DNS = 10,

  /**
   * Block for storing record data
   */
  GNUNET_BLOCK_TYPE_GNS_NAMERECORD = 11,

  /**
   * Block type for a revocation message by which a key is revoked.
   */
  GNUNET_BLOCK_TYPE_REVOCATION = 12,

  /**
   * Block to store a cadet regex state
   */
  GNUNET_BLOCK_TYPE_REGEX = 22,

  /**
   * Block to store a cadet regex accepting state
   */
  GNUNET_BLOCK_TYPE_REGEX_ACCEPT = 23,

  /**
   * Block for testing set/consensus.  If first byte of the block
   * is non-zero, the block is considered invalid.
   */
  GNUNET_BLOCK_TYPE_SET_TEST = 24,

  /**
   * Block type for consensus elements.
   * Contains either special marker elements or a nested block.
   */
  GNUNET_BLOCK_TYPE_CONSENSUS_ELEMENT = 25,
};


/**
 * Flags that can be set to control the evaluation.
 */
enum GNUNET_BLOCK_EvaluationOptions
{

  /**
   * Default behavior.
   */
  GNUNET_BLOCK_EO_NONE = 0,

  /**
   * The block is obtained from the local database, skip cryptographic
   * checks.
   */
  GNUNET_BLOCK_EO_LOCAL_SKIP_CRYPTO = 1
};


/**
 * Possible ways for how a block may relate to a query.
 */
enum GNUNET_BLOCK_EvaluationResult
{
  /**
   * Valid result, and there may be more.
   */
  GNUNET_BLOCK_EVALUATION_OK_MORE = 0,

  /**
   * Last possible valid result.
   */
  GNUNET_BLOCK_EVALUATION_OK_LAST = 1,

  /**
   * Valid result, but suppressed because it is a duplicate.
   */
  GNUNET_BLOCK_EVALUATION_OK_DUPLICATE = 2,

  /**
   * Block does not match query (invalid result)
   */
  GNUNET_BLOCK_EVALUATION_RESULT_INVALID = 3,

  /**
   * Block does not match xquery (valid result, not relevant for the request)
   */
  GNUNET_BLOCK_EVALUATION_RESULT_IRRELEVANT = 4,

  /**
   * Query is valid, no reply given.
   */
  GNUNET_BLOCK_EVALUATION_REQUEST_VALID = 10,

  /**
   * Query format does not match block type (invalid query).  For
   * example, xquery not given or xquery_size not appropriate for
   * type.
   */
  GNUNET_BLOCK_EVALUATION_REQUEST_INVALID = 11,

  /**
   * Specified block type not supported by this plugin.
   */
  GNUNET_BLOCK_EVALUATION_TYPE_NOT_SUPPORTED = 20
};


/**
 * Handle to an initialized block library.
 */
struct GNUNET_BLOCK_Context;


/**
 * Mingle hash with the mingle_number to produce different bits.
 *
 * @param in original hash code
 * @param mingle_number number for hash permutation
 * @param hc where to store the result.
 */
void
GNUNET_BLOCK_mingle_hash (const struct GNUNET_HashCode *in,
                          uint32_t mingle_number,
                          struct GNUNET_HashCode *hc);


/**
 * Create a block context.  Loads the block plugins.
 *
 * @param cfg configuration to use
 * @return NULL on error
 */
struct GNUNET_BLOCK_Context *
GNUNET_BLOCK_context_create (const struct GNUNET_CONFIGURATION_Handle *cfg);


/**
 * Destroy the block context.
 *
 * @param ctx context to destroy
 */
void
GNUNET_BLOCK_context_destroy (struct GNUNET_BLOCK_Context *ctx);


/**
 * Handle for a group of elements that will be evaluated together.
 * They must all be of the same type.  A block group allows the
 * plugin to keep some state across individual evaluations.
 */
struct GNUNET_BLOCK_Group;


/**
 * Create a new block group.
 *
 * @param ctx block context in which the block group is created
 * @param type type of the block for which we are creating the group
 * @param nonce random value used to seed the group creation
 * @param raw_data optional serialized prior state of the group, NULL if unavailable/fresh
 * @param raw_data_size number of bytes in @a raw_data, 0 if unavailable/fresh
 * @param ... type-specific additional data, can be empty
 * @return block group handle, NULL if block groups are not supported
 *         by this @a type of block (this is not an error)
 */
struct GNUNET_BLOCK_Group *
GNUNET_BLOCK_group_create (struct GNUNET_BLOCK_Context *ctx,
                           enum GNUNET_BLOCK_Type type,
                           uint32_t nonce,
                           const void *raw_data,
                           size_t raw_data_size,
                           ...);


/**
 * Serialize state of a block group.
 *
 * @param bg group to serialize
 * @param[out] nonce set to the nonce of the @a bg
 * @param[out] raw_data set to the serialized state
 * @param[out] raw_data_size set to the number of bytes in @a raw_data
 * @return #GNUNET_OK on success, #GNUNET_NO if serialization is not
 *         supported, #GNUNET_SYSERR on error
 */
int
GNUNET_BLOCK_group_serialize (struct GNUNET_BLOCK_Group *bg,
                              uint32_t *nonce,
                              void **raw_data,
                              size_t *raw_data_size);


/**
 * Destroy resources used by a block group.
 *
 * @param bg group to destroy, NULL is allowed
 */
void
GNUNET_BLOCK_group_destroy (struct GNUNET_BLOCK_Group *bg);


/**
 * Function called to validate a reply or a request.  For
 * request evaluation, simply pass "NULL" for the @a reply_block.
 * Note that it is assumed that the reply has already been
 * matched to the key (and signatures checked) as it would
 * be done with the #GNUNET_BLOCK_get_key() function.
 *
 * @param ctx block contxt
 * @param type block type
 * @param group block group to use for evaluation
 * @param eo evaluation options to control evaluation
 * @param query original query (hash)
 * @param xquery extrended query data (can be NULL, depending on type)
 * @param xquery_size number of bytes in @a xquery
 * @param reply_block response to validate
 * @param reply_block_size number of bytes in @a reply_block
 * @return characterization of result
 */
enum GNUNET_BLOCK_EvaluationResult
GNUNET_BLOCK_evaluate (struct GNUNET_BLOCK_Context *ctx,
                       enum GNUNET_BLOCK_Type type,
                       struct GNUNET_BLOCK_Group *group,
                       enum GNUNET_BLOCK_EvaluationOptions eo,
                       const struct GNUNET_HashCode *query,
                       const void *xquery,
                       size_t xquery_size,
                       const void *reply_block,
                       size_t reply_block_size);


/**
 * Function called to obtain the key for a block.
 *
 * @param ctx block context
 * @param type block type
 * @param block block to get the key for
 * @param block_size number of bytes in @a block
 * @param key set to the key (query) for the given block
 * @return #GNUNET_YES on success,
 *         #GNUNET_NO if the block is malformed
 *         #GNUNET_SYSERR if type not supported
 *         (or if extracting a key from a block of this type does not work)
 */
int
GNUNET_BLOCK_get_key (struct GNUNET_BLOCK_Context *ctx,
                      enum GNUNET_BLOCK_Type type,
                      const void *block,
                      size_t block_size,
                      struct GNUNET_HashCode *key);


/**
 * Update block group to filter out the given results.  Note that the
 * use of a hash for seen results implies that the caller magically
 * knows how the specific block engine hashes for filtering
 * duplicates, so this API may not always apply.
 *
 * @param bf_mutator mutation value to use
 * @param seen_results results already seen
 * @param seen_results_count number of entries in @a seen_results
 * @return #GNUNET_SYSERR if not supported, #GNUNET_OK on success
 */
int
GNUNET_BLOCK_group_set_seen (struct GNUNET_BLOCK_Group *bg,
                             const struct GNUNET_HashCode *seen_results,
                             unsigned int seen_results_count);


/**
 * Try merging two block groups.  Afterwards, @a bg1 should remain
 * valid and contain the rules from both @a bg1 and @bg2, and
 * @a bg2 should be destroyed (as part of this call).  The latter
 * should happen even if merging is not supported.
 *
 * @param[in,out] bg1 first group to merge, is updated
 * @param bg2 second group to merge, is destroyed
 * @return #GNUNET_OK on success,
 *         #GNUNET_NO if merge failed due to different nonce
 *         #GNUNET_SYSERR if merging is not supported
 */
int
GNUNET_BLOCK_group_merge (struct GNUNET_BLOCK_Group *bg1,
                          struct GNUNET_BLOCK_Group *bg2);


#if 0                           /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif

/* ifndef GNUNET_BLOCK_LIB_H */
#endif

/** @} */  /* end of group */

/* end of gnunet_block_lib.h */
